Disease and Insect Resistant Ornamental Plants: Syringa
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nysipm.cornell.edu 2018 hdl.handle.net/1813/56377 Disease and Insect Resistant Ornamental Plants Mary Thurn, Elizabeth Lamb, and Brian Eshenaur New York State Integrated Pest Management Program, Cornell University SYRINGA Lilac pixabay.com Syringa is a genus of about 30 species of lilac trees and shrubs native to Europe and Asia and widely grown as an ornamental in North America. For many, “lilac” brings to mind the common lilac, Syringa vulgaris, known for its fragrant masses of purple, lavender and white blooms in May. However, the common lilac is susceptible to several diseases and insects, including powdery mildew, bacterial blight, scale and borers. Some disease-resistant cultivars have been reported, and there are other less susceptible species and hybrids available. DISEASES Powdery Mildew is a common disease of lilacs caused primarily by the fungus Erysiphe syringae. Leaves of infected plants develop a whitish coating during the summer, and while it does not usually cause permanent damage, aesthetic quality can be greatly diminished. Cultivars of S. vulgaris are more susceptible than those of most other lilacs (8), and plants in shady sites with poor air circulation are more likely to be severely affected. Powdery Mildew Reference Species/Hybrids Cultivar Resistant Intermediate Susceptible Syringa diversifolia 4 Syringa emodi 4 Syringa julianae 4 Syringa meyeri 2, 4, 5 Syringa meyeri Dwarf Korean 6 Palibin 1, 5, 6, 9 Syringa meyeri ‘Bailbelle’ Tinkerbelle® 1, 2 Syringa microphylla 4 Syringa oblata var. dilatata 4 Powdery Mildew Reference Species/Hybrids Cultivar Resistant Intermediate Susceptible Syringa oblata ssp. dilatata Cheyenne 1 Syringa patula 4 Syringa persica 4 Syringa pubescens 3 ssp. microphylla Syringa pubescens Superba 4, 6, 9 ssp. microphylla Syringa pubescens Miss Kim 1, 6, 9 ssp. patula Syringa reflexa 4 Syringa reticulata 2, 3, 4 Syringa reticulata Ivory Silk 6, 9 Summer Snow 6, 9 Syringa swegiflexa 4 Syringa sweginzowii 4 Syringa villosa 4 Syringa vulgaris Adelaide Dunbar 6 Albert F. Holden 5 6 Agincourt Beauty 5 Alphonse Lavallee 6 A.M. Brand 6 Arch McKean 1, 6 Avalanche 6 Belle de Nancy 6 Charles Joly 6 Charles Tenth 6 Charm 6 Doyen Keteleer 4 Edith Cavell 6 Edmund Boisier 6 Excellens 4 Firmament 6 Henri Robert 6 Jules Ferry 4 Katherine Havemeyer 6 Krasavitska Moskvy 5 6 Laurentian 4 Leon Gambetta 6 Ludwig Spaeth 6 Powdery Mildew Reference Species/Hybrids Cultivar Resistant Intermediate Susceptible Syringa vulgaris Macrostachys 6 Marie Finon 6 Marie Legraye 6 Michael Buchner 6 Miss Ellen Wilmott 6 Mme. Antoine Buchner 6 Mme. F. Morel 6 Monge 6 Montaigne 6 Mrs. Harry Bickle 6 Mrs. W.E. Marshall 6 Paul Thirion 6 President Grevy 6 President Lincoln 6 President Poincare 6 Ruhm Von Horenstein 6 Sensation 5, 6 Silver King 6 Vauban 4 Vestale 6 Victor Lemoine 6 Wedgwood Blue 5 Yankee Doodle 6 Syringa yunnanensis 4 Syringa x chinensis 3* Syringa x chinensis Lilac Sunday 1 Rothomagensis 6 Syringa x henryi White Summers 6, 9 Syringa x hyacinthiflora Evangeline 1 Excel 6 Pocahontas 1, 6 Sister Justena 6 Syringa x josiflexa Agnes Smith 1 Anna Amhof 6, 9 Royalty 6, 9 Syringa x laciniata 2, 3 Syringa x prestoniae Donald Wyman 6, 9 Isabella 6 Powdery Mildew Reference Species/Hybrids Cultivar Resistant Intermediate Susceptible Syringa x prestoniae James McFarlane 6, 9 Minuet 1, 6, 9 Miss Canada 1 Nocturne 2 Syringa x Betsy Ross 7 Old Glory 7 Bacterial Blight of lilac, also known as shoot or blossom blight, is caused by the bacterium Pseu- domonas syringae pv. syringae. Favored hosts include S. vulgaris, S. x chinensis, S. reticulata, and S. x persica (8). Infections take place in the spring with wet conditions and first appear as brown spots which grow and coalesce into larger blotches. As the disease progresses, new shoots turn black and may be girdled resulting in death of shoots and blossoms. The bacterium will enter the plant through injury and often appears following late frost damage. Fresh pruning wounds, driving rain and even insects may spread this disease. Adequate spacing between plants can reduce spread of infection. Researchers at Tennessee State University evaluated 69 cultivars for resistance to multiple diseases, including bacterial blight, and report several resistant and susceptible cultivars. They also foundS. x josiflexa ‘Royalty’, S. pubescens ssp. patula ‘Miss Kim’, S. x prestoniae ‘Donald Wyman’ and S. vulgaris ‘Sensation’ to be resistant to both powdery mildew and bacterial blight (6). Bacterial Blight Reference Species/Hybrids Cultivar Resistant Susceptible Syringa meyeri Dwarf Korean 6 Syringa microphylla Superba 6 Syringa patula Miss Kim 6 Syringa reticulata Summer Snow 6 Syringa vulgaris Alphonse Lavellee 6 Edmund Boisier 6 Katherine Havemeyer 6 Krasavitska Moskvy 6 Michael Buchner 6 Mme. Antoine Buchner 6 Mrs. Harry Bickle 6 Sensation 6 Silver King 6 Victor Lemoine 6 Syringa x hyacinthiflora Excel 6 Syringa x josiflexa Anna Amhof 6 Royalty 6 Bacterial Blight Reference Species/Hybrids Cultivar Resistant Susceptible Syringa x prestoniae Donald Wyman 6 Isabella 6 Alternaria Blight of lilac caused by Alternaria alternata is a leaf disease that can cause significant damage on many lilac cultivars. Symptoms include brown spots which expand and coalesce into large blotches causing leaves to wilt, die and drop off. S. meyeri ‘Dwarf Korean’, ‘Palibin’ and S. vulgaris ‘Mme. Antoine Buchner’ are reported to be resistant in Tennessee (6). REFERENCES 1. Daughtrey, M., L. Mickaliger, L. Loizos, M. Tobiasz, and B. Seagraves. 2007. Evaluating lilac resis- tance to powdery mildew. Long Island Research and Extension Center 2007 Research Summaries. 2. Dirr, Michael A. 2009. Manual of woody landscape plants: their identification, ornamental charac- teristics, culture, propagation and uses. 6th ed. Stipes Publishing L.L.C., Champaign, IL. 3. Dirr, Michael A. 2011. Dirr’s Encyclopedia of Trees & Shrubs. 1st Ed. Timber Press, Inc., Portland, OR. 4. Hibben, C.R., J.T. Walker, and J.R. Allison. 1977. Powdery mildew ratings of lilac species and culti- vars. Plant Disease Reporter 61(3):192-196. 5. “Lilacs.” Chicago Botanic Garden. chicagobotanic.org/plantinfo/lilacs 6. Mmbaga, M.T., R.J. Sauve, E. Nnodu, and S. Zhou. 2005. Multiple disease resistance to powdery mildew, bacterial blight, and Alternaria blight in lilacs (Syringa spp.). J. Arbor. 31(1):1-9. 7. Pooler, M.R. 2008. ‘Betsy Ross’, ‘Old Glory’, and ‘Declaration’ lilacs. HortScience 43(2):544-545. 8. Sinclair, W., and H.H. Lyon. 2005. Diseases of Trees and Shrubs. 2nd Ed. Cornell Univ. Press, Ithaca, NY. 9. Windham, M.T., W.T. Witte, R.J. Sauve, and P.C. Flanagan. 1995. Powdery mildew observations and growth of lilac in Tennessee. HortScience 30(4):813. OTHER RESOURCES “Missouri Botanic Garden.” missouribotanicalgarden.org “Woody Plants Database.” Urban Horticulture Institute, Cornell University. woodyplants.cals.cornell. edu/plant/search Cornell Cooperative Extension Produced by the New York State Integrated Pest Management Program, which is funded through Cornell University, Cornell Cooperative Extension, the New York State Department of Agriculture and Markets, the New York State Department of Environmental Conservation, and USDA-NIFA. Design by Karen English, New York State IPM Program. Cornell Cooperative Extension provides equal program and employment opportunities. © 2018Cornell University and the New York State IPM Program. Posted 4/2018 at hdl.handle.net/1813/56377 nysipm.cornell.edu.